Baseball and softball players continually search for better bats to improve their hitting performance. Bat performance is generally based upon length, weight, moment of inertia (MOI) and impact response during contact with the ball. Manufacturers have made attempts to improve the impact response during contact with the ball using a variety of constructions of materials. Unfortunately, each of these prior attempts has various shortcomings.
As manufacturers have improved bats, various regulatory bodies that administer or organize baseball or softball games have placed restrictions on bat performance and configuration. In general, these rules limit the maximum rebound speed of a ball from the barrel portion of the bat. In order to limit the maximum response of the bat, manufacturers have modified their designs to dampen the response to all impacts. In other words, these designs reduce the responsiveness of the bat at both low impact speeds as well as high impact speeds. Typically, this is done by adding material to the thickness of the barrel portion of the bat to increase the hoop stiffness. This results in hindering the hitting performance of less skilled players in an effort to control the maximum rebound speed generated by the best players.
Bat rebound performance is generally maximized at a narrow width of the barrel commonly referred to as the “sweet spot.” The prior art includes several attempts to produce a bat with reduced performance at the sweet spot. The intent to these designs has been to level the impact response along a greater width of the barrel, effectively widening the perceived “sweet spot.” These attempts have several shortfalls. For example, U.S. Pat. No. 6,949,038, issued to Fritzke, discloses increasing the wall thickness of the barrel near the sweet spot. This is accomplished, for example, by including an insert 22, as illustrated in FIG. 4, having first and second tubular wall transition regions 36 and 38, as well as an intermediate tubular region 40, having an increased thickness. Additionally, as illustrated with respect to FIG. 7, an intermediate tubular region 140 provided on the outside surface of the bat would have an increased thickness. As can be appreciated, the added thickness of the insert or the outer portion of the bat would add additional weight and create stress concentrations at each end of the thicker regions.
In recent years, many bat manufacturers have begun to produce bats using fiber reinforced plastic (FRP) materials. For example, the patent application publication to Van Nguyen, uses a bat body made from a composite material, such as fiberglass, carbon fibers, or a combination of glass and carbon fibers. The use of FRP materials has allowed manufacturers to independently tailor the stiffness characteristics of each portion of the bat. For example, using FRP materials would allow manufacturers to make the handle quite stiff, resulting in less bending, while allowing the barrel portion to be more flexible in the radial or “hoop” direction. However, current approaches to using FRP materials in bats have resulted in a record of poor durability. While FRP materials are quite strong in tension, they are relatively weak in compression. During impact with a ball, the primary forces on the surface of the bat barrel are compressive. For this reason, cracking in the barrel portion of current FRP bats is quite common.
Consequently, there is a need to provide an improved bat which would meet regulation standards for maximum barrel response with less dampening at slower speed impacts. The improved bat would use FRP materials in a way which optimizes their benefits, but avoids the durability issues of existing products.
Additionally, there is a need to produce a bat having a more consistent impact response along the length of the barrel than conventional bats without the increased weight or the creation of stress concentrations, as described in prior art references.